No one can predict consistently when market declines will happen.

It’s easy to look back today and say with hindsight that the stock market was overvalued at a particular time and due for a decline. But no one has been able to accurately predict market declines on a consistent basis.

In January 1973, a New York Times poll of eight market authorities predicted that the market would “move somewhat higher” in the future. The Dow industrials proceeded to decline 45% over the next 23 months. Then, although almost no one predicted it, the Dow rose 38% in 1975.

No one can predict how long a decline will last.

Since 1982, with few exceptions, market declines have been relatively brief. Earlier market declines have lasted longer.

After the 1929 crash, it took investors 16 years to restore their investments if they invested at the market high. In 2000, it took about five years. But after the 1987 crash, it took about 23 months to get back. In 1990, it took about eight months. (In all cases, dividends were assumed to be reinvested.)

No one can consistently predict the right time to get in or out of the market.

Successful market timing during a decline is extremely difficult because it requires a pair of near-perfect actions: getting out and then getting back in at the right time.

A common mistake investors make is to lose patience and sell at or near the bottom of a downturn. But even if you have decent timing and get out early in a decline, you still have to figure out when to get back in.

A bear market is not usually characterized by a straight-line decline in stock prices. Instead, the market’s downward trend is likely to be jagged — showing bursts of stock price increases, known as “sucker’s rallies,” and then declines.